1. Field of the Invention
This invention relates broadly to apparatus for protecting occupants of vehicles in crashes or in sudden positive or negative accelerations. More specifically, it relates to anthropomorphic dummies or manikins intended to simulate human occupants in testing for the effectiveness of protective equipment. The term "biofidelic" has been coined to describe mechanical structures that attempt to duplicate biological structures with high accuracy of fidelity.
2. Background of the Invention
The development of dummies is discussed in U.S. Army Report USARTL-TR-79-22B, AIRCRAFT CRASH SURVIVAL DESIGN GUIDE, Volume II, Applied Technology Laboratory, U.S. Army Research and Technology Laboratories (AVARADCOM), Fort Eustis, Va. 23604 (980). This report is expressly incorporated by reference herein. One of the earliest dummy designs was a rugged ejection seat dummy built by Sierra Engineering Company for the Air Force in 1949. This dummy had limited articulation and poor biomechanical fidelity, but it was used by aircraft system manufacturers, and by automobile manufacturers. Another early dummy was designed and built by Swearingen. This was a 120-lb dummy with articulated principal joints, a realistic distribution of body weight, and a center of gravity approximating that of the human body. This dummy was used to evaluate the effect of an explosive decompression of an aircraft cabin as a result of a window failure. In 1951 Swearingen completed an improved dummy, capable of withstanding accelerations of 35 to 50 G. This dummy was used in evaluating a new safety harness for aircraft. In 1954 Alderson Research Laboratories, Inc. created the first mass production dummy, unique for its modular design, which permitted new parts to be added as needs changed. By 1967 dummy manufacturers achieved some improvement in biomechanical response with increased articulation in the vertebral column and shoulders and increased chest compliance. In 1968 the Society of Automotive Engineers ("SAE") Recommended Practice J963 defined the first standard dummy, a 50th-percentile male anthropomorphic test dummy with specified weights, center-of-gravity locations, dimensions for body segments, and ranges of motion for body joints.
In 1971 the National Highway Traffic Safety Administration formally changed the role of dummies from that of determining the relative performance of similar safety systems to that of an absolute measuring instrument for determining the potential for injury to human occupants in an automobile crash. In 1972 General Motors Corporation produced a 50th-percentile male anthropomorphic test dummy. The design of the Hybrid II was based on the torso and limbs of an advanced Alderson dummy (Model No. VIP-50A), with modifications to the chest to allow damping and increased deflection of the chest. The head assembly was adapted from a Sierra design (Model No. 292-1050) with several anatomical modifications. The neck and the lumbar spine are butyl rubber cylinders, with an internal steel cable reinforcing the spine. With further modifications, the Hybrid II dummy was the basis for the standards in the Code of Federal Regulations, Title 49, Part 572. These standards included the dimensions and inertial properties of the dummy.
In 1975 General Motors produced the Hybrid III dummy. This dummy had much improved component biofidelity, especially in the head and neck system, the torso, and in the distribution of the weight in the lower torso. It was also provided with transducers for measuring neck loads and chest deflections. The Hybrid III head is an aluminum skull covered by a vinyl skin.
The Hybrid III neck was designed to provide biomechanical response in flexion (the head and neck rotating forward) and in extension (the head and neck rotating backward). The Hybrid III neck consists of three rigid aluminum vertebral elements molded in a butyl elastomer. The Hybrid III neck is shown in FIG. 1. It comprises a top plate 101, a bottom plate 102 and intermediate plates 103 molded in butyl elastometer 104. The elastomer provides the high damping characteristics required to effectively model the human response. Aluminum end plates attach the neck segment to the head and torso. A steel cable runs through the center of the neck.
The foregoing summary of the development of test dummies demonstrates that they have been designed primarily for applications in automobiles. One of the main concerns in automobile crashes is the response of the neck to impacts from the forward and lateral directions. These dummies are not truly adequate for ejection seat testing, because ejection seat dummies are subjected to sudden vertical accelerations as well as to horizontal acceleration.
Anthropomorphic models used in ejection seat testing are commonly referred to as "manikins" instead of dummies, because these models are much more sophisticated representations of the human body. Test manikins have been developed specifically for ejection seat testing by the Armed Services. The Advanced Dynamic Anthropomorphic Manikin (ADAM), described in ADAM--THE PHYSICAL BEING, by Richard P. White, Jr., presented at the 25th Annual SAFE Symposium, Las Vegas, Nev., Nov. 16-19, 1987, retains the Hybrid III neck, and thus has a neck structure with limited biofidelity in its response to vertical and horizontal accelerations.
The Hybrid III neck system cannot faithfully model the motion of the human head, because the Hybrid III neck system is designed so that the moment applied to the head of the Hybrid III manikin is a function of the angle between the head and the neck, instead of being a function of the angle between the head and the torso.